Lecture Notes for General Biology BI 101 - Energy in Biological Systems


I Energy in Biological Systems

A) Fundamentals to understanding Energy
	1) Energy exists in different forms - heat, light, chemical energy, and electrical energy
		Energy - ability to do work
		Thermodynamics - science of the transformation of energy
	2) Laws of Thermodynamics
		Conservation of energy - energy can be transferred or transformed but cannot be created or destroyed
			Biomass powerplant converts energy from wood into electricity
			Plant converts light energy into checmical energy
		Entropy (measure of disorder or randomness)
			Systems tend to become more random in terms of dispersed energy until reaching equilibrium
			low entropy = ordered system (example - cells in biological systems use energy to maintain order)
			high entropy = system in disorder, random
			Energy conversions (see below) tend to increase entropy or disorder
			Applies to biological systems where energy is lost as heat from the system to the surroundingss
		Enthalpy (H) - measure of total energy (usually heat) within a system
			Exergonic - reaction that releases Gibbs free energy (reactants have more energy than the product)
				Exothermic - reaction where heat energy is lost from the system to the surrounding environment
			Endergonic - reaction where Gibbs free energy is gained (product has more energy than the reactants)
				Endothermic - reaction where heat is absorbed by the system from the surrounding environment
	3) Potential energy (energy that is available but has not been used) 
		Water behind a dam (potential to flood)
		Snow on top of a hill (potential for avalanche)
		Chemicals in the body have potential energy - based on energy within the chemical structure of molecules
	4) Kinetic energy (energy of motion)
		Cells convert potential energy of chemicals into kinetic energy used by the cell
		Moving objects can perform work by transferring motion
B) Energy Needs of all organisms
	1) Where does it come from - making and breaking glucose
	2) Energy = capacity to do work
		Light, Heat, Chemical forms
	3) Chemicals involved in Energy in Biological systems
		ATP, Glucose, Enzymes - lower the energy of activation
	4) Energy pathway
	5) Glucose is made by photosynthesis
	6) ATP is made by breakdown of glucose = cellular respiration
		ATP + X ------- ADP + XP + energy = phosphorylation
	7) Energy used in various activities
C) Photosynthesis - making glucose and energy for the entire ecosystem
	1) Picking apart the reaction
		a) Light Dependent reaction (Involves ENERGY)
			Light energy from different wavelengths that make up the light spectrum
		b) Light Independent reaction (Involves CO2)
		c) Long term energy storage (Involves Glucose conversion)
		d) takes place in the chloropasts in the cells of the leaves
		e) Chloroplast in detail 
		f) Where do gases enter and leave for photosynthesis - stomata of leaves
D) Light Dependent - using different wavelengths of light
	1) Excitation of chlorophyll and other pigments by light energy (photons)
		a) different wavelengths of light spectrum carry energy for photosynthesis
		b) e- move and create energy (ATP) for Light Independent reaction - chemiosmosis
		c) e- stripped from H2O molecules, O2 is liberated as a gas
		d) plants have many pigments for capturing light energy, masked by 
			dominance of green chlorophyll, appear during fall - fall foliage spectacle
			1) Some sites keeping track of fall foliage
				Various states
					Foliage Network
					U. S. Forest Service
				Vermont
					Vermont fall foliage1
					Vermont fall foliage 2
				Maine
					Maine foliage
					State of Maine -fall foliage
				New Hampshire
					New Hampshire foliage
					Weirs Online cam
	2) Plants enhance their ability to collect light energy through pigments
		a) When do we see these pigments - fall foliage 
E) Light Independent
	1) Calvin cycle: uses ATP and three molecules of CO2 attaches to a 3C molecule made from RuBP
	2) Leads to the production of 3C molecules, some go back into Calvin 
		cycle, others go to make glucose
F) Long term energy storage 
	1) Glucose=monosaccharide, used to make polysaccharides which are 
		often stored in underground tubers (examples = scroll down to see slides of potatoes, 
		turnips, etc..., or fruits) 
G) Cellular Respiration - breaking glucose down and using the energy to make ATP 
		(phosphorylation)
	1) Relationship between respiration and cellular respiration
			breathing in oxygen to make water and energy
	2) Two step process - Glycolysis, Krebs Cycle (only for aerobic organism
H) Glycolysis
	1) Initial breakdown of glucose into two 3C pyruvic acid molecules, 
			pyruvic acid dissociates into pyruvate ions
	2) Pyruvate has three options depending on whether the organism breathes O2 or not
		a) Alcohol Fermentation, production of alcohol (ETOH) and CO2
		b) Lactic Acid Fermentation, production of lactic acid and CO2
		c) Krebs Cycle (see below)
I) Krebs Cycle
	1) Pyruvate is modified with CoA to make AcetylCoA
	2) AcetylCoA enters the Krebs Cycle (2C molecule) into the mitochondrion
	3) Becomes attached to a 4C molecule and becomes 6C molecule 
	4) 6C molecule is gradually broken down into a 4C molecule 
	5) CO2 is released and e- are taken into the e- transport system
	6) Energy for ATP production occurs in the e- transport system
	7) Glucose is not the only source of energy used to produce ATP in the Krebs Cycle
		How other chemicals enter the Krebs cycle


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Copyright © 2001 Jay Pitocchelli. All rights reserved. The contents of this page are the intellectual property of Dr. Jay Pitocchelli for distribution to students enrolled in General Biology BI 01 at Saint Anselm College. These pages may not be copied, photocopied, reproduced, translated, or published in any electronic or machine-readable form in whole or in part without prior written approval of Jay Pitocchelli. Students enrolled in General Biology BI 01 at Saint Anselm College have permission to print this material for their lecture notes. The images linked to this web page are the sole property of Addison Wesley/ Benjamin Cummings Publishers™.